High Hopes and Broken Dreams
The interplay of climate change, natural hazards, and the mortality of
high mountain expeditions in the Nepalese Himalayas
2025-04-30 @ EGU Erik Kusch & Christian H Mohr 1
Erik Kusch & Christian H. Mohr
Introduction
2025-04-30 @ EGU 2Erik Kusch & Christian H Mohr
First ascent of Mt. Everest without Oxygen
First ascent of Cho Oyu
First ascent of Mt. Everest
First solo ascent of Mt. Everest without Oxygen
First women to summit Mt. Everest
First summitting of all 14 peaks at >8,000 masl by one person
First summitting of all 14 peaks at >8,000 masl by one person in a single season
Mallory’s body is discovered
Snowstorm conditions kill 12 on Mt. Everest
Avalanche kills 11 on Manaslu
Avalanche kills 15 on Manaslu
Serac collapse and other causes kill 11 on K2
Extremes
Catastrophic hazards leading to a high risk of death.
Seasons
Weather conditions governing summit bid windows.
Climate
Ice and glacier movement, coverage, and depth.
Study Approach
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Data:
• ERA5-Land
• Climate Reanalysis
• 1950-Today
• 9x9km resolution
• Relevant climate variables
• Himalayan Database
• 480 peaks
• 11,400+ expeditions
• 89,000+ members
• 15,900+ literature records
Methods:
• Climate Data Retrieval and Handling with KrigR
• Bayesian Models with BRMS
Extremes
Climate
Seasons
Erik Kusch & Christian H Mohr
temperature
snowfall
windspeed
Death & Success at 8,000 masl
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Mortality rates
increase over time
Summit bid windows shrink over time.
Climate and
weather may
explain this!
General Conditions
Trends in annual mean (μ) and standard
deviation (σ):
Changing Conditions in the Himalayas
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Extremes
Climate
Seasons
Erik Kusch & Christian H Mohr
1. Air temperatures are warming
2. Snow depth decreases
3. Windspeeds at summits increase
• Destabilization of glaciers and seracs
• Larger build-up of more fragile cornices
General Conditions
Seasonal mean and standard deviation:
Changing Conditions in the Himalayas
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Extremes
Climate
Seasons
Erik Kusch & Christian H Mohr
Stability of:
1. Snowfall decreases more pre-monsoon
2. Windspeed decreases more pre-monsoon
The pre-monsoon season has become less favourable for
mountaineering expeditions than the post-monsoon season.
Intensity of:
1. Snowfall increases pre-monsoon,
but decreases post-monsoon
2. Windspeed increases in both seasons,
but becomes more variable pre-monsoon
Snowstorm likelihood increases in pre-monsoon season.
Short-term Weather Stability
Autocorrelative coefficient of daily conditions per
season for several lag lengths:
Changing Conditions in the Himalayas
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Extremes
Climate
Seasons
Erik Kusch & Christian H Mohr
The pre-monsoon season has become less favourable for
mountaineering expeditions than the post-monsoon season.
More Post-Monsoon Expeditions
More Pre-Monsoon Expeditions
Changing Conditions in the Himalayas
2025-04-30 @ EGU Erik Kusch & Christian H Mohr 8
Extremes
Climate
Seasons
Number & Length of Extreme Events
Count of (consecutive) days exceeding
5% and 95% range of seasonal values
Pre-Monsoon mountaineering at increased risk
from (snow) storms
1. More extreme temperatures and longer
heatwaves post-monsoon
Post-Monsoon mountaineering at increased risk
of heatwaves, avalanches, and serac collapses
2. More extreme high snowfall amounts pre-
monsoon
3. More extreme high windspeeds pre-
monsoon
Catastrophic Events in Mountaineering
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Extremes
Climate
Seasons
Shorter summit
bids reduce chance
of experiencing
hazards
Unexpectedly, risk
of storms and
avalanches
decreases!
Not all
events
will have
been
reported
…
Implications & Further Work
2025-04-30 @ EGU Erik Kusch & Christian Mohr 10
Local infrastructure, legislation, and
expedition practices ought to accommodate.
Himalayan mountaineering schedules
respond strongly to changes in seasonal
weather conditions.
Expedition planning ought to plan and prepare
for hazards depending on season.
Pre- and post-monsoon mountaineering
seasons pose divergent hazards to
expeditions.
Traffic and rescue preparedness ought to be
re-evaluated for each summit.
Himalayan summits are not subject to
homogenous weather and climate trends.
Further work is required utilizing more precise
and complete data sources.
Untangling what leads to success and death
in Himalayan mountaineering requires further
investigation.
2025-04-30 @ EGU Erik Kusch & Christian Mohr 11
Erik Kusch (PhD)
Advisor
Center for International Climate Research
erik.kusch@cicero.oslo.no | www.erikkusch.com
Graphic profile
Christian H. Mohr (PhD)
Group Leader Eng. Geol. Hazard Assess.
Federal Institute for Geosciences and Natural
Resources (BGR) & University of Potsdam
christian.mohr@bgr.de
Contact us with Questions or Suggestions!
